Methyl acetate, reaction data

Fig. 9.2.3 Methyl acetate reaction data, including standard Raman spectra of acetic acid, methanol and methyl acetate. The acid catalyst used in this reaction was cone, sulfuric acid.

Other companies (e.g., Hoechst) have developed a slightly different process in which the water content is low in order to save CO feedstock. In the absence of water it turned out that the catalyst precipitates. Clearly, at low water concentrations the reduction of rhodium(III) back to rhodium(I) is much slower, but the formation of the trivalent rhodium species is reduced in the first place, because the HI content decreases with the water concentration. The water content is kept low by adding part of the methanol in the form of methyl acetate. Indeed, the shift reaction is now suppressed. Stabilization of the rhodium species and lowering of the HI content can be achieved by the addition of iodide salts. High reaction rates and low catalyst usage can be achieved at low reactor water concentration by the introduction of tertiary phosphine oxide additives.8 The kinetics of the title reaction with respect to [MeOH] change if H20 is used as a solvent instead of AcOH.9 Kinetic data for the Rh-catalyzed carbonylation of methanol have been critically analyzed. The discrepancy between the reaction rate constants is due to ignoring the effect of vapor-liquid equilibrium of the iodide promoter.10... 

The rate of saponification of methyl acetate at 25C was studied by making up a solution 0.01 molar in both base and ester and titating the mixture at various times with standard acid. The data are tabulated. Show that the reaction is second order and find the specific rate. 

The use of Eq. (5) to fit data recorded using a microcalorimeter was first demonstrated by Bakri (6), who studied the acid hydrolysis of methyl acetate in hydrochloric acid. In that experiment, 1 mmol of methyl acetate was added to 2mL of 1 N hydrochloric acid solution in a glass ampoule. The experimental data were fitted to Eq. (5) using a least squares analysis which gave k = 0.116 x 10-3 sec-1 and AH= 1.98 kJmol-1. In this paper, Bakri also shows how the method may be applied to both second-order, solution phase A+B x reactions and to flow calorimetry. 

The hydrolysis of methyl acetate is an autocatalytic reaction and is first order with respect to both methyl acetate and acetic acid. The reaction is elementary, bimolecular and can be considered irreversible at constant volume for design purposes. The following data are given ... 

The endothermic maxima observed for apolar solutes and salts in water-rich mixtures must also contribute towards the minima in AH for alkaline ester hydrolysis in these mixtures. As before, the tendency for the rate constant to decrease is determined by the behaviour of 5m AS. Plots of AH against AS are complicated but in mixtures for which x2 < xf the data points generally fall on a straight line. Of course, there are new problems in this class of reactions. For example, the possibility arises that the rate constant is a function of quantities describing the equilibrium between, say, RO- and OH". However, the patterns which emerge indicate that this may not usually be an important consideration in water-rich mixtures. One exception may be the alkaline hydrolysis of ethyl acetate and methyl acetate (Tommila and Maltamo, 1955) in methyl alcohol + water mixtures for which AH increases gradually as x2 increases. 

Reaction of bromomethane (CH3Br) with the nucleophile acetate (CH3COO") affords the substitution product methyl acetate with loss of Br as the leaving group (Equation [1]). Kinetic data show that the reaction rate depends on the concentration of both reactants that is, the rate equation is second order. This suggests a bimolecular reaction with a one-step mechanism in which the C-X bond is broken as the C—Nu bond is formed. 

The following mechanism for the hydrolysis of methyl acetate in a strong base is consistent with the experimental data for the reaction. 

The Raman results of the first reaction were promising and the raw data from that reaction are shown in Fig. 9.2.4(a) graphically, illustrating the changing intensities of the Raman peaks of the reactants methanol (1040 cm peak) and acetic acid (890 cm peak) compared with the peaks for the product methyl acetate (850 and 1050 cm ). Figme 9.2.4(b) is a principle components analysis (PCA)... 

Reactive distillation (RD) is a key opportunity for improving the structure of a process [1, 2]. The combination of distillation and reaction is possible, of course, only if the conditions of both operations can be combined. This means that the reactions have to show data for reasonable conversions at pressure and temperature levels that are compatible with distillation conditions. The type of catalysis is also important. Homogeneous catalysis is possible in most cases but needs a separation step to recycle the catalyst. This can be avoided in heterogeneous catalysis, but here special constructions are necessary to fix the catalyst in the reaction zone. If everything harmonizes, considerable advantages arise for the production of methyl acetate via RD, for example, only one column is needed instead of nine and a reactor (Fig. 2.1). 

All of these conclusions are in agreement with observations 170a) on the cleavage of triethylboron in glyme by substituted benzoic and acetic acids. The reaction is first order in each, and plots of log k vs. pK, gives a positive slope, such that the strotiger acids react less rapidly. Addition of DMSO retards the rate, while addition of methyl acetate or trifluoroacetic acid do not affect the rate of reaction. These data, coupled with an isotope effect [RCOOH/RCOOD] knjk = 2, are suggestive of the mechanism... 

We have developed a non equilibrium model for multi component reactive separation techniques. This model is solved numerically by a sure and stable strategy. The originalities of this model are the Maxwell Stefan formulation which is solved in this complete formulation and the absence of restrictive assumptions concerning the reaction. To validate the model, an experimental pilot has been developed. It is a part of column where inlet flux are controlled, and local accurate temperatures and compositions profiles are measured. For each experiments, which concern the production of methyl acetate, the results of steady state simulation are in good agreement with the experimental data and demonstrate the importance to take into account the reaction in the diffiisionnal layer. So, the non equilibrium model seems to be a well adapted toll for the simulation, design and optimisation of reactive distillation. 

In some cases, a reaction may seem to be first order even though we know two species are involved. These rates are called pseudo-first-order reactions and can occur when the concentration of one of the reactants is in great excess. Consider the following data from Ref. [7] (with permission). A reaction flask is set up containing methyl acetate and 1 M HCl at 25°C. The almost unspoken second reactant is the water in the HCl solution which is of the order of 55 M in H2O. Actually the HCl is a catalyst and is not consumed during the reaction but aids the hydrolysis. 

The products of the reaction of OH with DiPE have been investigated by Wallington et al. (1993a) and by Collins et al. (2005). In the presence of NO c, Wallington et al. (1993a) observed essentially unity yields of both isopropyl acetate and the sum of formaldehyde, methyl nitrite, and methyl nitrate. Reaction of OH with DiPE is expected to occur mainly at the tertiary CH—O— sites. Eor example, Wallington et al. estimate 80% of the reaction occurs at the tertiary site on the basis of kinetic data for related species such as MTBE, while the Kwok and Atkinson estimation method predicts > 98% of the reaction will occur at the tertiary site. As first described by Wallington et al., reaction at the tertiary site can clearly lead to the observed products ... 

The reaction of chlorine atoms with methyl acetate has been the subject of absolute rate studies by Notario et al. (1998) and Cuevas et al. (2005) and a relative rate study by Christensen et al. (2000). The rate coefficient data are summarized in table VII-B-14 and are plotted in figure VII-B-11. The values of A (C1 CH30C(0)CH3) measured by Notario et al. (1998) and Cuevas et al. (2005) are approximately 25% higher than those measured by Christensen et al. (2000). As described previously, Wallington et al. (2006a) have argued that there may have been secondary loss of chlorine atoms via... 

Titrimetric analysis is a classical method for generating concentration-time data, especially in second-order reactions. We illustrate with data on the acetylation of isopropanol (reactant B) by acetic anhydride (reactant A), catalyzed by A-methyl-imidazole. The kinetics were followed by hydrolyzing 5.0-ml samples at known times and titrating with standard base. A blank is carried out with the reagents but no alcohol. The reaction is... 

The most accurate data on isomer distributions in alkylation of heterocycles have been obtained from the reaction of 3-n-butylpyridine with methyl radicals in acetic aeid. The ratio of the monomethyl products was determined by infrared spectroscopy and gas chromatography and is showm in (27). A small amount of 2,6-dimethyl-3-n-butylpyridine was also obtained. These ratios again show a high proportion of ortho substitution. 

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